In the past metal corrosion caused by conventional motor fuels such as gasoline was not much of a problem because such hydrocarbon fuels are inherently non-corrosive. However, with the advent of fuels containing alcohols such as gasohol or straight alcohol fuels, corrosion has become a major problem because such fuels are corrosive. It has been reported that this corrosion is due to the presence of acidic contaminants in such fuels such as formic acid. It is almost impossible to avoid such contaminants because they occur in fuel grade alcohols and are also formed in storage as normal alcohol oxidation products.
It is known from U.S. Pat. No. 2,993,772 that alkenyl succinic acids as well as their anhydrides inhibit and/or prevent the deposit-forming tendency of hydrocarbon fuels during combustion and/or modify the deleterious effect of the formed deposits in both leaded and unleaded fuels particularly in gasoline and jet fuels. The substituted imidazoline co-additives of this invention, more fully described hereafter, also are known compounds and have found use, for example, in motor fuel compositions to prevent carburetor icing as disclosed in U.S. Pat. No. 3,036,902. It has now been discovered that a combination of the substituted imidazolines of the present invention with a monoalkenylsuccinic acid wherein the alkenyl group contains about 8 to 30 carbon atoms provides corrosion inhibiting properties to fuels containing alcohols such as gasohol or straight alcohol fuels.